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1.
The Personal Presence System (PPS) is an experimental research prototype platform to support advanced broadband applications,
including multimedia conferencing and distance learning. It supports the user's presentation control of advanced network elements
(multimedia bridges). The multimedia bridge provides for a single contact point per user, who receives only one combined video
stream, which minimizes access bandwidth. This architecture solves the -squared transmission problem of multipoint video conferencing and makes customer terminal equipment simpler and cheaper than
high-end desktop workstations. The PPS provides each user with flexible presentation control of a feature-rich video bridge.
The PPS also supports advanced features such as object extraction and multimedia object associations. 相似文献
2.
As multimedia applications spread widely, it is crucial for programming and design support systems to handle “time” in multimedia
documents effectively and flexibly. This paper presents a set of interactive system support tools for designing and maintaining
the temporal behavior of multimedia documents. The tool set provides mechanisms for anomaly detection, temporal query processing,
and interactive scheduling. It is based on a fast incremental constraint solver we have developed, which can be adapted by
any constraint-based system. The incremental constraint solver provides immediate feedback to the user, supporting a highly
interactive design process. Combined with existing optimal layout generation mechanisms proposed in the literature, our tools
effectively utilize the flexibility provided by constraint-based systems. 相似文献
3.
Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared
by different individuals and organizations. In this paper, we present an algebra for creating and querying interactive multimedia
presentation databases. This algebra operates on trees whose branches reflect different possible playouts of a set of presentations.
The algebra not only extends all the classical relational operators to such databases, but also introduces a variety of novel
operators for combining multiple presentations. As our algebra supports merging parts or all of existing presentations, this
algebra can also be used as an authoring tool for creating multimedia presentations. We prove a host of equivalence results
for queries in this algebra, which may be used to build query optimizers for interactive presentation databases. 相似文献
4.
In this paper, we investigate a playout scheduling framework for supporting the continuous and synchronized presentations
of multimedia streams in a distributed multimedia presentation system. We assume a situation in which the server and network
transmissions provide sufficient support for the delivery of media objects. In this context, major issues regarding the enforcement
of the smooth presentation of multimedia streams at client sites must be addressed to deal with rate variance of stream presentations
and delay variance of networks. We develop various playout-scheduling algorithms that are adaptable to quality-of-service
parameters. The proposed algorithms permit the local adjustment of unsynchronized presentations by gradually accelerating
or retarding presentation components, rather than abruptly skipping or pausing the presentation materials. A comprehensive
experimental analysis of the proposed algorithms demonstrates that our algorithms can effectively avoid playout gaps (or hiccups)
in the presentations. This scheduling framework can be readily used to support customized multimedia presentations. 相似文献
5.
Adaptive multimedia synchronization in a teleconference system 总被引:3,自引:0,他引:3
In this paper, we present an adaptive buffering scheme for implementing intra-stream and inter-stream synchronization in
real-time multimedia applications. The essence of the proposed scheme is to dynamically enforce equalized delays to incoming
media streams, in order to piece-wise smooth the network delay variations and to synchronize the streams at the sink. An adaptive
control mechanism based on an event-counting algorithm is employed to calibrate the PlayOut Clocks (POCs), which manages the
presentations of multimedia data. The algorithm does not rely on globally synchronized clock and makes minimal assumption
on underlying network delay distribution. Also, the user defined quality of service (QoS) specifications can be directly incorporated
into the design parameters of the synchronization algorithm. The proposed synchronization scheme has been experimentally implemented
in a teleconference system which consists of separately controllable audio, video, and data channels. The modular structure
of the synchronization control provides the flexibility to maintain an arbitrary synchronization group in conjunction with
a distributed conference management scheme. This paper also shows the experimental results of the test implementation and
the suitability of the proposed scheme with respect to the multimedia traffic across an FDDI/Ethernet network. 相似文献
6.
Denise J. Ecklund Vera Goebel Thomas Plagemann Earl F. Ecklund Jr. 《Multimedia Systems》2002,8(5):431-442
In this paper, we present a separable, reusable middleware solution that provides coordinated, end-to-end QoS management
over any type of service component, and can use existing (legacy) QoS management solutions (by using wrappers) in a distributed
multimedia system. Our middleware solution incorporates strategic and tactical QoS managers, and supports protocols and messages
between tactical managers and managed application components, and between QoS managers in the management hierarchy. Strategic
QoS managers take a global view of QoS provided by a set of application components within the manager's policy domain. Tactical
QoS managers provide local control over application components. We introduce the concept of QoS policy domains to scope the
authority of a strategic QoS manager. We describe how the management hierarchy is dynamically configured and reconfigured
based on runtime needs of the application. 相似文献
7.
Nevzat Hurkan Balkir Gultekin Ozsoyoglu 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(4):294-307
Most multimedia servers reported in the literature are designed to serve multiple and independent video/audio streams. We
think that, in future, multimedia servers will also serve complete presentations. Multimedia presentations provide unique
opportunities to develop algorithms for buffer management and admission control, as execution-time consumption requirements
of presentations are known a priori. In this paper, we examine presentations in three different domains (heavyweight, middleweight,
and lightweight) and provide buffer management and admission control algorithms for the three domains. We propose two improvements
(flattening and dynamic-adjustments) on the schedules created for the heavyweight presentations. Results from a simulation
environment are presented.
Received June 9, 1998 / Accepted October 13, 1998 相似文献
8.
A multimedia application involves information that may be in a form of video, images, audio, text and graphics, need to be
stored, retrieved and manipulated in large databases. In this paper, we propose an object-oriented database schema that supports
multimedia documents and their temporal, spatial and logical structures. We present a document example and show how the schema
can adress all the structures described. We also present a multimedia query specification language that can be used to describe
a multimedia content portion to be retrieved from the database. The language provides means by which the user can specify
the information on the media as well as the temoral and spatial relationships among these media. 相似文献
9.
Eve M. Schooler 《Multimedia Systems》1996,4(5):210-225
As integrated services have become available to the desktop, users have embraced new modes of interaction, such as multimedia
conferencing and collaborative computing. In this paper, we provide a survey of past and present research that has influenced
this application area, and describe research directions for the future. 相似文献
10.
Multimedia streams such as audio and video impose tight temporal constraints for their presentation. Often, related multimedia
streams, such as audio and video, must be presented in a synchronized way. We introduce a novel scheme to ensure the continuous
and synchronous delivery of distributed stored multimedia streams across a communications network. We propose a new protocol for synchronized playback and compute the buffer
required to achieve both, the continuity within a single substream and the synchronization between related substreams. The
scheme is very general and does not require synchronized clocks. Using a resynchronization protocol based on buffer level
control, the scheme is able to cope with server drop-outs and clock drift. The synchronization scheme has been implemented
and the paper concludes with our experimental results. 相似文献
11.
The next generation of interactive multimedia documents can contain both static media, e.g., text, graph, image, and continuous
media, e.g., audio and video, and can provide user interactions in distributed environments. However, the temporal information
of multimedia documents cannot be described using traditional document structures, e.g., Open Document Architecture (ODA)
and Standard Generalized Mark-up Language (SGML); the continuous transmission of media units also raises some new synchronization
problems, which have not been met before, for processing user interactions. Thus, developing a distributed interactive multimedia
document system should resolve the issues of document model, presentation control architecture, and control scheme. In this
paper, we (i) propose a new multimedia document model that contains the logical structure, the layout structure, and the temporal
structure to formally describe multimedia documents, and (ii) point out main interaction-based synchronization problems, and
propose a control architecture and a token-based control scheme to solve these interaction-based synchronization problems.
Based on the proposed document model, control architecture, and control scheme, a distributed interactive multimedia document
development mechanism, which is called MING-I, is developed on SUN workstations. 相似文献
12.
K. Selçuk Candan Eric Lemar V.S. Subrahmanian 《The VLDB Journal The International Journal on Very Large Data Bases》2000,9(2):131-153
Abstract. Though there has been extensive work on multimedia databases in the last few years, there is no prevailing notion of a multimedia
view, nor there are techniques to create, manage, and maintain such views. Visualizing the results of a dynamic multimedia
query or materializing a dynamic multimedia view corresponds to assembling and delivering an interactive multimedia presentation
in accordance with the visualization specifications. In this paper, we suggest that a non-interactive multimedia presentation
is a set of virtual objects with associated spatial and temporal presentation constraints. A virtual object is either an object, or the result of a query.
As queries may have different answers at different points in time, scheduling the presentation of such objects is nontrivial.
We then develop a probabilistic model of interactive multimedia presentations, extending the non-interactive model described
earlier. We also develop a probabilistic model of interactive visualization where the probabilities reflect the user profiles,
or the likelihood of certain user interactions. Based on this probabilistic model, we develop three utility-theoretic based
types of prefetching algorithms that anticipate how users will interact with the presentation. These prefetching algorithms
allow efficient visualization of the query results in accordance with the underlying specification. We have built a prototype
system that incorporates these algorithms. We report on the results of experiments conducted on top of this implementation.
Received June 10, 1998 / Accepted November 10, 1999 相似文献
13.
I. Mirbel B. Pernici T. Sellis S. Tserkezoglou M. Vazirgiannis 《The VLDB Journal The International Journal on Very Large Data Bases》2000,9(2):111-130
Abstract. When authoring multimedia scenarios, and in particular scenarios with user interaction, where the sequence and time of occurrence
of interactions is not predefined, it is difficult to guarantee the consistency of the resulting scenarios. As a consequence,
the execution of the scenario may result in unexpected behavior or inconsistent use of media. The present paper proposes a methodology
for checking the temporal integrity of interactive multimedia document (IMD) scenarios at authoring time at various levels.
The IMD flow is mainly defined by the events occurring during the IMD session. Integrity checking consists of a set of discrete
steps, during which we transform the scenario into temporal constraint networks representing the constraints linking the different
possible events in the scenario. Temporal constraint verification techniques are applied to verify the integrity of the scenario,
deriving a minimal network, showing possible temporal relationships between events given a set of constraints.
Received June 9, 1998 / Accepted November 10, 1999 相似文献
14.
One of the challenges in the design of a distributed multimedia system
is devising suitable specification models for various schemas in
different levels of the system.
Another important research issue is
the integration and synchronization of heterogeneous multimedia
objects. In this paper, we present our models for multimedia schemas
and transformation algorithms. They transform high-level
multimedia objects into schemas that can be used to
support the presentation and communication of the multimedia objects.
A key module in the system is the Object Exchange Manager (OEM). In this paper,
we present the design and implementation of the OEM module,
and discuss in detail the interaction
between the OEM and other modules in a
distributed multimedia system. 相似文献
15.
We describe a system for generating and controlling sound effects from within applications. We discuss performance demands
and current technology constraints on sound synthesis methods, highlight several distinct interactive control strategies,
and demonstrate a development environment for making a large database of heterogeneous sound models manageable by developers
who are not sound synthesis experts. 相似文献
16.
Recent advances in computer technologies have made it feasible to provide multimedia services, such as news distribution
and entertainment, via high-bandwidth networks. The storage and retrieval of large multimedia objects (e.g., video) becomes
a major design issue of the multimedia information system. While most other works on multimedia storage servers assume an
on-line disk storage system, we consider a two-tier storage architecture with a robotic tape library as the vast near-line
storage and an on-line disk system as the front-line storage. Magnetic tapes are cheaper, more robust, and have a larger
capacity; hence, they are more cost effective for large scale storage systems (e.g., video-on-demand (VOD) systems may
store tens of thousands of videos). We study in detail the design issues of the tape subsystem and propose some novel tape-scheduling
algorithms which give faster response and require less disk buffer space. We also study the disk-striping policy and the
data layout on the tape cartridge in order to fully utilize the throughput of the robotic tape system and to minimize the
on-line disk storage space. 相似文献
17.
The single-system approach is no longer sufficient to handle the load on popular Internet servers, especially for those offering
extensive multimedia content. Such services have to be replicated to enhance their availability, performance, and reliability.
In a highly replicated and available environment, server selection is an important issue. In this paper, we propose an application-layer
broker (ALB) for this purpose. ALB employs a content-based, client-centric approach to negotiate with the servers and to identify
the best server for the requested objects. ALB aims to maximize client buffer utilization in order to efficiently handle dynamic user
interactions such as skip, reverse presentation, go back in time. We also present details of a collaborative multimedia presentation
platform that we have developed based on ALB. 相似文献
18.
Wen-Syan Li K.Selçuk Candan Kyoji Hirata Yoshinori Hara 《The VLDB Journal The International Journal on Very Large Data Bases》2001,9(4):312-326
Due to the fuzziness of query specification and media matching, multimedia retrieval is conducted by way of exploration.
It is essential to provide feedback so that users can visualize query reformulation alternatives and database content distribution.
Since media matching is an expensive task, another issue is how to efficiently support exploration so that the system is not
overloaded by perpetual query reformulation. In this paper, we present a uniform framework to represent statistical information
of both semantics and visual metadata for images in the databases. We propose the concept of query verification, which evaluates queries using statistics, and provides users with feedback, including the strictness and reformulation alternatives
of each query condition as well as estimated numbers of matches. With query verification, the system increases the efficiency
of the multimedia database exploration for both users and the system. Such statistical information is also utilized to support
progressive query processing and query relaxation.
Received: 9 June 1998/ Accepted: 21 July 2000 Published online: 4 May 2001 相似文献
19.
Minos N. Garofalakis Banu Özden Avi Silberschatz 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(4):206-225
The Enhanced Pay-Per-View (EPPV) model for providing continuous-media services associates with each continuous-media clip
a display frequency that depends on the clip's popularity. The aim is to increase the number of clients that can be serviced
concurrently beyond the capacity limitations of available resources, while guaranteeing a constraint on the response time.
This is achieved by sharing periodic continuous-media streams among multiple clients. The EPPV model offers a number of advantages
over other data-sharing schemes (e.g., batching), which make it more attractive to large-scale service providers. In this
paper, we provide a comprehensive study of the resource-scheduling problems associated with supporting EPPV for continuous-media
clips with (possibly) different display rates, frequencies, and lengths. Our main objective is to maximize the amount of disk
bandwidth that is effectively scheduled under the given data layout and storage constraints. Our formulation gives rise to
-hard combinatorial optimization problems that fall within the realm of hard real-time scheduling theory. Given the intractability
of the problems, we propose novel heuristic solutions with polynomial-time complexity. We also present preliminary experimental
results for the average case behavior of the proposed scheduling schemes and examine how they compare to each other under
different workloads. A major contribution of our work is the introduction of a robust scheduling framework that, we believe,
can provide solutions for a variety of realistic EPPV resource-scheduling scenarios, as well as any scheduling problem involving
regular, periodic use of a shared resource. Based on this framework, we propose various interesting research directions for
extending the results presented in this paper.
Received June 9, 1998 / Accepted October 13, 1998 相似文献
20.
In this paper, we present two novel disk failure recovery methods that utilize the inherent characteristics of video streams
for efficient recovery. Whereas the first method exploits the inherent redundancy in video streams (rather than error-correcting
codes) to approximately reconstruct data stored on failed disks, the second method exploits the sequentiality of video playback
to reduce the overhead of online failure recovery in conventional RAID arrays. For the former approach, we present loss-resilient
versions of JPEG and MPEG compression algorithms. We present an inherently redundant array of disks (IRAD) architecture that combines these loss-resilient compression algorithms with techniques for efficient placement of video streams
on disk arrays to ensure that on-the-fly recovery does not impose any additional load on the array. Together, they enhance
the scalability of multimedia servers by (1) integrating the recovery process with the decompression of video streams, and
thereby distributing the reconstruction process across the clients; and (2) supporting graceful degradation in the quality
of recovered images with increase in the number of disk failures. We present analytical and experimental results to show that
both schemes significantly reduce the failure recovery overhead in a multimedia server. 相似文献